The social adequacy index (S A I) is an average of the percentage of words heard correctly at the three standard levels of speech and is suitable for measuring the improvement of hearing by a hearing aid or by any surgical procedures, and is also suitable for medicolegal purposes. The S A I for hearing in 150 cases of patients with hearing impairment was observed and the following results were obtained. 1) In 90% of patients with conductive hearing loss, the S A I was greater than 61. The S A I was less than 70 in 87% of mixed deaf cases and in 81% of perceptive deaf cases respectively. The majority of conductive deaf cases showed relatively great index comparing with the other types of deafness. 2) By comparison of the grade of subjective hearing difficulty with the S A I for the Korean speech hearing, the present author indicated the limit of normal hearing at S A I=94, the threshold of social adequacy at S A I=35, the “beginning of social difficulty” at S A I=68 and the “limit of compensation” at S A I=10 or 15. 3) The correlation between the pure-tone hearing loss and the S A I yielded a negative correlation. Of three types of deafness, the conductive deafness showed the correlation between the average of three pure-tone decibel losses, at 500, 1000 and 2000 cps, and the S A I to be statistically most significant (p<0.01). In perceptive deafness, the average of four pure-tone decibel losses, at 500, 1000, 2000 and 4000 cps, showed statistically more significant correlation (P<0.01) with the S A I than the average of three pure-tone decibel losses at 500, 1000 and 2000 cps. The present author constructed a table of the S A I for all combinations of the hearing loss for speech and the minimum discrimination loss, and formulated a table of disability ratings for hearing impairments.